Covered rubber thread



Oct. 27, 1942. 5 VAN voo -us 2,300,241

COVERED RUBBER THREAD Filed Jar 1. 8, 1941 Patented Oct. 27, 1942 UNITEDSTATES PATENT OFFICE COVERED RUBBER THREAD George S. Van Voorhis,Easthampton, Mass, assignor to United Elastic Corporation, Easthampton,Mass.,- a corporation of Massachusetts Application January 8, 1941,Serial No. 373,591

4 Claims. (01. 57-140) mined degree. Usually two such layers of yarn arewound around the core, one outside the other, the second layer beingwound reversely to the first so that the twist of one will beneutralized by the other.

The most common use of covered rubber thread is in the manufacture ofbraided, knit, or woven fabrics. It has long been recognized in thetrade, however, that no two pieces of elastic webbing have exactly thesame degree of stretch or elongation. This objectionable characteristicof fabrics of this type is well illustrated in corsets, girdles, orsimilar articles, where one side will stretch more easily than the otherso that as the garment is worn it stretches more and more in localizedareas, and finally becomes practically worthless.

With a view to remedying this condition it was proposed some years agoto lay a stretch-limiting or stay thread of cotton, or other textilefiber, be-

with relatively few turns per foot of length, around the core during thethread covering operation, so that this non-elastic thread would beincluded in the covering with the rubber thread.

break relatively easily, especially under a quick snap. It is a commonexperience, therefore, to find that elastic webbing made of coveredrubber threads in which these stay threads are incorporated will, aftera period of severe wear, and particularly if subjected to sudden strainsin the nature of snap actions, begin to lose their smoothness anduniformity. Such a piece of webbing will exhibit pin-holes where thestay threads have broken and the advantages of such threads, of course,are lost at and adjacent to thepoints of rupture.

The present invention is especially concerned.

with these conditions and it aims to devise a covered rubber thread inwhich this difficulty will be largely eliminated. v

The nature of the invention will be readily understood from thfollowingdescription when read in connection with the accompanyingdrawing, and the novel features will be particularly pointed out in theappended claims.

In the drawing,

Figure 1 is a side view, on a large scale, showing a short section ofcovered rubber thread with the covering partly unwound therefrom;

Fig. 2 is a cross-sectional view, also on a large scale, of the threadshown in Fig. 1; and

Fig. 3 is a similar view showing a slight modification. side the rubbercore, or to wind it loosely, and '30 Referring first to Figs. 1 and 2,the article there shown comprises a rubber core 2 which may be either ofsquare, circular, or other suitable crosssectional form, and a fibrousthread or yarn 3 lying beside it. The inner and outer layers or By thismeans the extent to which the covered wrappings of covering yarn orthread are shown rubber thread could thereafter be stretched orelongated was permanently and definitely limited to the length of thestay thread.

This improvement in covered rubber thread has been of great value inenabling manufacturers 40 to predetermine and control the degree ofstretch of elastic fabrics, and consequently, to produce fabrics whichwill retain their original smoothness for a longer period of wear andgreatly reducing the liability of the goods becoming over-stretched inlocalized areas and thus causing them to lose their shape.

In making covered rubber thread of thecharacter just described, however,it has been necessary to use stay threads of small size, that is,

those of high count or dernier. As a practical matter, also, cotton orrayon threads have been found best suited to this purpose. Even these,however, fail often to perform the functions for which they areintended, largely because they that a stretch-limiting thread of nylonneed not at 4 and 5, respectively.

I have found that if the stretch-limiting element 3 consists of a threadof suitable strength which is relatively non-elastic but still has avery limited degree of elasticity, the difficulty above described issuccessfully avoided. Such a thread is rarely broken by a sudden snap,apparently for the reason that it has a certain shock-absorbing actionor quality which cushions or nullifies the breaking effect of a quicksnap. Those threads made of polymerized polyamides, of which nylon isthe best known commercial example, answer this purpose verysatisfactorily. Nylon yarn is readily available commercially and whileit is slightly more expensive than cotton thread, the quantity used forstay thread purposes is so limited that the difference in price is notan important commercial factor. A nylon thread is stronger than a cottonthread of the same size so be 'as large as one of cotton, and, inaddition, it has the important advantage of beingrelatively immune frombreakage under suddenly applied stresses which would certainly break acotton thread. In other words, while the cotton thread has a sharp. andcomparatively definite breaking point, the nylon thread does not, buthas a limited degree of elasticity which serves to absorb shock and thusto prevent breakage under a sharp snap of the type above referred to.Such degree of elasticity is relatively low, permitting perhaps not overabout 15% of elastic elongation, whereas a rubber thread may bestretched 50( l% or 800%.

If desired, the advantages of both the cotton and nylon threads can reay be combined by including a stretch-11m thread of cotton,

together with the nylon thread 3, in a covered rubber assembly of thecharacter above described. This is illustrated in Fig. 3. The cottonthread,

said core and enclosed in said cover with said core in astretch-limiting relationship thereto. said nylon thread having alimited degree 01'- elasticity but being devoid of a sharp breakingpoint. whereby it serves to limit the extent of stretch of the rubberthread without breaking under a sharp snap.

2. A covered rubber thread, comprising a rubber core, a flexible coverof fibrous thread or yarn wound around said core, and a stretch-limitingthread of nylon extending along said rubber core and enclosed therewithin said cover, said nylon thread having a limited degree of elasticitybut being of a fibrous nature, has the advantage of exhibiting lesstendency to pull back into the cover when it is broken than would anylon thread, since the latter has a smoother, more slippery surface.

The invention thusprovides a covered rubber thread much superior tothose heretofore produced in :performing those functions for which in:the same. and a nylon thread extending alon 40 I being devoid of a sharpbreaking point, whereby it serves to limit the extent of stretch of therubber thread without breaking under a sharp snap.

3. A covered rubber thread, comprising a rubber core, a flexible covercomprising reversely wound layers of fibrous thread or yarn enclosingsaid rubber core, one of said layers being wound around the other, and anylon thread extending along said core and enclosed in said cover, withsaid rubber core in a stretch-limiting relation ship thereto, said nylonthread having a limited degree of elasticity but being devoid of a sharpbreaking point, whereby it serves to limit the extent of stretch of therubber thread without breaking under a sharp snap. I

4. A covered rubber thread, comprising a rubber core, a flexible coverof fibrous thread or parn wound around said core, and twostretch-limiting threads, one of nylon and the other of fibrousmaterial, extending along said rubber core and enclosed therewith insaid cover, said nylon threadhaving a limited degree of elasticity butbeing devoid of a sharp breaking point, whereby it serves to limit theextent of stretch of the rubber thread without breaking under a sharpsnap.

GEORGE s. VAN ,voomns.

